This invention relates to demineralized bone and to an osteogenic composition incorporating demineralized bone. More particularly, the invention relates to demineralized bone particles having a relatively high median length to median thickness ratio, e.g., as in the case of filaments and thin sheets, and to a flowable osteogenic composition containing such particles within a biocompatible fluid carrier.
The use of demineralized bone powder in the repair of bone defects has been a subject of investigation for some time. Bone powder contains one or more substances, possibly bone morphogenic protein (BMP), which induce bone regeneration at the defect site. See, e.g., Covey et al., "Clinical Induction of Bone Repair with Demineralized Bone Matrix or a Bone Morphogenetic Protein", OrthoRaedic Review, Vol. XVII, No. 8, pp. 857-863 (August, 1989). According to Habal et al., "Autologous Corticocancellous Bone Paste for Long Bone Discontinuity Defects: An Experimental Approach", Annals of Plastic Surgery, Vol. 15, No. 2, pp. 138-142 (August 1985), autogenous bone which has been granulated into a pastelike material and combined with autogenous blood has been used in the repair of long bone defects in dogs.
While it is known that bone particles possessing relatively high median length to median thickness ratios, e.g., filaments and thin sheets, can be obtained by milling bone, such particles are not known to have been subjected to demineralization, a process which results in the nearly complete removal of the inorganic components of the bone, largely hydroxy apatite, which gives bone its characteristic rigidity and structural properties.
U.S. Pat. No. 5,073,373 discloses a deformable, shape-sustaining osteogenic composition, suitable as a filler for osseous defects, in which particles of demineralized bone are uniformly distributed within a carrier which is a liquid polyhydroxy compound such as glycerol. The vast majority of the demineralized bone particles possess random, irregular geometries with an average median length to median thickness ratio of from about 1:1 to about 3:1.